Constant tension line-tensioning mechanism

ABSTRACT

Constant line tension can be maintained in a ship&#39;&#39;s mooring or towing line extending from a winch by supplying to a polyphase phase-wound induction motor driving the winch alternating current from an alternating-current source the frequency of which is variable in response to the load on the winch. Such variablefrequency source may be an alternator driven by a phase-wound induction machine powered to operate as a motor. The variablefrequency AC source is connected to the winch motor to drive the winch only in the reeling-in direction, but the tension on the line can retard the motor speed or stall the motor or rotate the winch and motor in the opposite, paying-out direction against the reeling-in torque of the motor. The winch motor torque can be adjusted by varying the value of resistance shunted across the rotor winding of the winch motor. The line can be retrieved very quickly by having a squirrel-cage alternating-current motor connected mechanically to the phase-wound induction machine. During constant-line-tension operation, such motor is simply idly rotated with such machine, but for rapid line retrieval the motor can be powered by the same AC supply as powers the phase-wound induction machine and such motor will then drive the phase-wound induction machine positively to operate as an alternator. During such operation the field windings of the phase-wound electrical machine are connected in reverse phase relationship to the AC supply and the rotor windings are connected to the stator windings of the winch motor. Also, for towing applications the voltage of the variable-frequency source can be altered in response to variations in the length of line paid out or reeled in to control the winch motor in turn in response to sensing the extent of rotation of the winch drum in paying out or reeling in the towing line and correspondingly varying the field excitation of the alternating-current generator supplying current to the winch motor to operate the winch motor for restoring the line to its original length.

c 221' Filed: I

21 Appl; No.: 301,208

v 57] Constantline tension can be maintained ina ships [United StatesPatent [19 1 O strom i 1 CONSTANT TENSION LlNE-TENSIQNING MECHANISM][75] Inventor: Cyrus Os trom, Seattle, Wash. i [7 3] Assignee:ConsolidatedElectric Corporation,

16 3] Continuation-in-part oflserz No. 099,575, Dec. 1

52 u.s.c1. .'...254/1-72,3l8/6 51 Int.Cl "new 1/48 58] 1 Field ofSearch)"; 254/150, 186 R 172, 1 254/173 15 1 netcr nc s c itea;UNITED-STATESPATENTSf; I

l/l9 69 os trom 254/172 Primary Examinen-EvomC l Bl unk 1 AssistantExaminer lames L.,Rowland Attorney Robert w. Beach ABSTRACT mooring ortowing lineextending'from a winchby supplying to a polyphase"phase-wound inductionmotor driving the winchalternatingcurrent from analternating-current source the frequency of which is variable inresponse to the load on the winch. Such variable-frequency source may bean alternator driven by a phase-wound induction machine powered tooperate as a motor The variable-frequency AC source is a connected tothe winch motor to drive thewinch only in the reeling-in direction, butthe tension on the line can retard themotor speedor stall the motor orrotate the winch aridmotor in the opposite,paying-out direction againstthe reeling-in torque of the motor. The

winch motor torque can beadjusted by varying the value ofresistanceshunted acrossthe rotor winding of the winch motor. The linecan be retrieved very quickly by having a squirrel-cagealternating-current motor connected mechanically torthe phase-woundinduction machine. During constant-line-tension operation, such motor issimply idly rotated with such ma chine, but for rapid line retrieval themotor can be powered by the same AC supply as powersthe phasewoundinductionTrnachine and such motor will then a drive the phase-woundinduction machine positively to v V operate as an alternator, Duringsuch operation the 1 field windings of the phase-wound electricalmachine are connected in reverse phase relationship to the AC supply andthe rotor windings are connected to the I stator windings of the winchmotor Also, for towing applications the voltage of "thevariable-frequency source can be alteredin response to variations in theI length of line paid out or reeled in to control the winch motor inturn in response to sensing the extent 1 of rotation of the winch drumin paying out or reeling in the towing line and correspondingly jvaryingthe":

field excitation of the altemating-current generator supplying currenttor the winch motor to'o perate the winch motor for restoring the lineto its original length. 7 i c 6 Claiins,3 Drawing Figures D C K0701?F/ELD EXC/TA T/ON CUEEE/YT SOURCE 'plicationSer. No. 099,57 5.y'Particularlywhen the mechanismisused in connec- I t-ion with a linefor mooring a ship, but also when it isused in connection with'a linefor towing, itis anobject i CONSTANT TENSION LINE-TENSIONING MECHANISM Ii application is a continuation-impart of my application Ser. No.099,575, filed De c. l'8,1l-970,for Constant Tension Line-Tensioning"Mechanism; The present inventionyrelatesi.to:thefgeneraltype of Icontinual line-tensioning mechanism disclosed in U. S. Pat; No.3,421,736, and the general purpose of the present invention is to makemechanism of that type i a more useful and versatile. 1

Mechanism of the general type disclosedin said U. S.

Pat. "No. 3,42l,736 canalso be utilized for maintaining a substantiallyconstant tension in a lineconnecting a tug and its tow, as an operationalternative to using I such mechanism'formaintaining a substantiallyconstanttension in a ships mooring line, asdisclosed in apto be abletooverride the automatic tension-control V mechanism and to vreel in linevery rapidly when'it has 4 been cast off I "FIG. 1 is a diagrammatic topperspective of the bow portion era ship and a dock portiontowhichtheship is moored in conjunction with the wiring diagram of a ship'winchdrive motor and. a regulated power supply for such motor. i 4 i I FIG. 2is a diagrammatic top perspective of the stern portion of a tug and the.bow portion ofa barge tow inenergized the brake-releasing solenoid willbe gized so that the brake band will be clamped by its spring to thebrake drum so as tosecure thewinch drumagainst rotation. 1

The winchmotor 5 is of the polyphasephase-wound sourcecan be connectedin a different phase relationa "While the startingiswitches 9 and 10determine in I which'direction the'winch motor 5 and the drum of winch 4will turn, the speed andtorque of the motor; in a either direction willbe determined by the manner in v i i which the phase-wound coilsof therotor 11 are c on-. y Y

nected together. Such rotorwindings are-interconfl ship throughreversingswitch 10 to the'stator winding 75f the motor so'as to causethe roto'r'of thernotor to turn in a direction s uchtha t the winchdrum4 pays out mooring line .2.

nected" by wires, 12, but such wiresinclude invthem teroonnected bytowing Jlinein conjunction with-a v wiring diagram of a shipwinchdriVemotor; at

FIG; 3 is a diagramshowing the'relationship of and connectionsbetweenvarious components of themechanism including the 'winch,power supply forthe' winc'h and control rnechanismfor suchpower supply. 7

The mechanismillustrated in the drawings exerts on I a line," such as amooring'line or aitowing line of aship,

a selected substantially-constant line tension. Suchlinehaulingmechanism can be controlle 'so t'hat the tension on the linecan be alte i edat will to reei' in or pay out the line and the speed ofoperation or torque of the line-winding means can-be altered at will.This invention has particularly advantageous application to the winch of'a ship mooring line or towing line and, consequently, the inventionwill be described with reference to these applications, although it willbe understood that such rnechanismcanfbe used in any type ofinstallation in whichit is desiredto maintain a substantiallyconstantline tension'where the variationjinlength of I the ine islimited.

in FIG. 1 of the drawings the foredeck of a ship 1 is i illustrated fromwhicha line 2jextends to a bollard 3 on a dock. The line 2istensionedbyline-winding'means,

illustratedas a deck winch 4to which a winch motor 5 is connected. Whenthe winch motoris not'in opera- ,tion, the winch drum is securedwagainstrotation by brake 6 as indicatedinFlG. '3. Such brakecan be of the drumand band type inwhich the brake band is held in position clamping thebrake drum by compression spring means. The clamping action of theIbrake drum is released automatically by anelectric solenoid con,-

. nected incircuit with thewinchlmotor 5 so that-when thewinch motor isenergized the brake solenoid will be energized simultaneously to releasethebraking action.

Correspondingly, when the winch driving 'motoris deslidewire resistanceswhich can be bridged at different locations by a set of interconnectedadjustable brushes 12". These brushes can be movedconjointly along theslide wires,l2' in corresponding positions, or"' the connections tothe,resistances can be-in the form of Y taps and connectorscanconnecttogether correspond i f f ing taps of the, respective resistances12' to provide an i 3 equivalent variation in resistance value.

To operate'the winch 4 in a normal operation effect ing mooring of aship', therefore, theswitch 9can be closed to energizethetniotor 5 forreeling in the moor ing line 2 orthe switch :10 can be closed toenergize the motor s for driving the winch 4 to. pay out the line 2 iand the bridging connections 12" can be setto decrease the effectiveresistancein the, rotor connections for increasing'the speed and/ortorque of the momno any desired value within the capability. of "themotor.

When the ship has been brought into its desired mooringposition theswitches 9 and 10 are openedand the switch 9' is closed to connect thestator winding 7 of the winch motor S'continuously toa load-responsivevariable-frequency AC source 8" instead of tothe con stant-frequency Acsource 8 to which' the motor was connected by the switch 9 or the switch10, to provide the desired operation for maintaining 'a substantially;

constant line tension. e I g i The winding 7 of the winch motors can beAC source in a direction tofpay out line, although as will be discussedhereinafter, if sufficient tension is eX- erted on-the line 2 the winch4 and winch motor Snot onlycan be stopped but can be turned by the lineten-f sion in a reverse or overhauling direction to enable line to beunreeled from the drum of winch 4 eventhough torque is beingapplied'continuously to that drum by 1 the motor 5 tending to reel inthe line.

deenerco-nnected to the variable frequency AC source 8 only by i theswitch 9 representing rotation of the motor and l winch 4 in areeling-in direction. More specifically, the motor cannot be connectedto the variable-frequency Whether the motor 5, when the switch 9' isclosed,

will turn winch. 4 in a direction to reel in line 2, or will be'stopped,or actually will beturned reversely so that winch 4 will payout line 2,depends upon the degree of torque-exerted'by the motor on the winchdrum.

Such torque; in turn, depends upon the'power con-. sumed by the motorand the amount of power consumed is governed by the amount of resistance12 in i I the connections between the coils of the rotor-11. The

greater the mount of resistance the less current will flow, the lesswill be the power absorbed by the motor and the smaller will be thetorque developed by the motor. I

e As in the operation of the motor 5 whenit is connected to theconstant-frequency AC supply 8, it is also desirable to beable to alterthe amount of resistance in the connections of rotor 11 when the motoris 'connected. to the variable-frequency AC source 8'. The

- same resistance-adjusting mechanism can be used for altering theamount of the resistances 12' between the speed ofoOO r.p.m.to produce30-cyclealternating current. I

The coils of the alternator rotor 19 must be excited so as to magnetizethe rotor for developing'electricity in the stator; windings connectedto the output line 21. Excitation current is supplied to the coils ofthe altemator rotor 19 from a DCsource 22 which, conveniently, may berectified 'AC. lncreasein electrical loading of the alternator reflectedby an increase in current passing through the output leads 21 to thewinch motor 11, because of the increase in mechanical torqueload on suchmotor and the winch 4, will tend toreduce the speed of the alternator.Reduction in speed of the alternator would result in a decrease inoutput voltage and a reduction in frequency. The reduction in frequencywould correspond directly to the rotorcoils 11 and the bridging wires12" when current is' supplied to the motor from thesource 8. Alteringthe amount of effective resistance in the connections between the rotorwindings will, however, not have as great an effect on the torqueexerted by the winch.

motor when it is connected to the variable-frequency AC source 8' aswhen the motor is connectedvto the constant-frequency source .8 becausethe'power consurned bythe motor depends not only onthe resistance in therotor circuit, but also on the frequency and voltage applied to thestator winding 7.

to'the mechanical torque load on the motor 5, which creases and thestator current increases, it is desirable for the frequency of thecurrent supplied'to the motor to drop so as to enable the motor 5 tohave the type of foperating characteristics desired, namely,characteristics of high torque but low speed. Consequently, it ispreferred that the maximum frequency of the variablefrequency source8"b'e considerably lower than the frequency of the constant-frequencysource 8. Instead of being 60 cycles per second, therefore, the maximumfrequency of the source 8 can, for example, be half f "As indicated inFIG. 1, it is desirable for the freuency of the AC source 8 tobevariable in response that value, namely, 30 cycles per second. As theme- 7 chemical torque load increases on the mooring which and motor, thefrequency can be reduced progressively with increase in load to a valuein the range of 15 to 20 v cycles and the input voltage can drop from220 volts to creases. a g

While the load-responsive variable-frequency AC source 8' can be ofvarious types, F IG. 1 illustrates such a power source which has provento be quite satisfactory. Such source is a motor-generator set,including a polyphase phase-wound induction machine powered to operateas a motor 13 connected to drive an alternator 14. The stator windings15 of such motor can .be coni nected by aswitch 16 to the-shippowersupply 8,-such "as three-phase 60-cycle current having 440 voltage. 'Thecoils of rotor 17 areinterconnected by wires 18 1 having in themresistances 18". The degree of effective resistance can be selected oradjusted forealibration purposes by bridging wires18" which can be setsothat under no load the alternator 14 will be turned at the l20'or 130volts, forexample, while the current'inis reflected in the currentsupplied to the stator wind- 3 ings 7. As the mechanical torque load onthe motor inreduction in alternator rotor speed.

An'increase in load on mooringline 2 resulting from a tendency of theship to move away from the mooring bollard 3 increases the mechanicaltorque load on the winch 4 and winch motor 5 so as to increase thedemand for current flowing through the stator coils of such, motor winchare continuously-connected to the variable-frequency AC source-8 whilethe ship is being maintained in moored condition. Such increase incurrent must besuppliedfromthe outputleads connected to the statorwindings 20 of alternator 14 so as to increase the electric power loadon, the alternator. As

tion motor is that its speed is reduced as the mechanical torque load,on it is increased and, consequently, such a motor is suitable fordriving thealternatorl4 to maintain a substantially constant tension onthe winch line when such line is attached to'the bollard 3 or otherobject. When the line is cast off,however, it is desirable to be abletoincrease the speed-of the winch motor 5 and the winch 4 to reel in theslack line very quickly to prevent the trailing line from being fouledin propellers or bow thrusters or from becoming snagged. The presentinvention provides an arrangement which will enable motor 5 to berotated in a reeling-in direction at approximately twice the speed thatsuch motor would turn if its field 7 were connected directly to the 440-volt powersupply line 8 byopening switch 9' and closing' switch 9. a v

The mechanismto accomplish such high-speed reeling in rotation of winchmotor 7 includes an alternating current three-phase squirrel cageinduction motor 34,

having itsshaft permanently connected to the shaft of rotor 17 of thepolyphase phase-wound induction motor 13. The stator of motor 34 canbeconnected to the 440-volt, -cycle supply line 8 by a three-poleswitch, 35. Three additional switches. are provided, namely, switch 36between the rotor winding 17 'of motor 13 and the resistances of theresistance grid bank 18", switch 37 between the stator winding 15 ofmotor 13 and the supply; line 8, but in reversed phase relationship to,switch 16', and switch 38 for connecting leads the rotor :17. a

.motor 34 under virtuallyno load.

. connectedto the stator windingsw7'of winch motor current supplied toit for a given voltage, and, second,

the polyphase phaseewound induction machine13 is capable of beingsupplied with electricity'to operate as a motor and, alternatively, iscapable of being. driven mechanically to operate astan alternator.

During constant-tension operation of the system, as

- hasbee'n explained abov e'gthe switch 16 will be closed to. supplyO-cycle alternating currentfrorn the supply line 8 to thestatorwinding'l5 of the electrical machine 39 from the rotorwinding 170f, motorl3 m lead-8'40" synchronous speed at which the rotor 17 would{be turned in the clockwisedirection if switch 16 were closed, or in thecounterclockwise direction if switch 37 were closed. A representativespeed would be;900

rpm; It will be noted thatit is unnecessary to stop theelectrical-machine 13 in orderto convertfrom the c'on 13,50 as todriveitsrotor17electricallyas a motor for .1 turning the rotor 19 fofalternator 14." Such rotation of the alternator rotor willeffectgeneration of alternating current in the fieldwinding 20, which will besupplied through the closed switch-9 to the field winding 7of the winchmotor 5. During suchopera tion rotation of willcorrespo ndingly rotatethe rotor of Whenfit is desired to cbnvert'the operation of motor .5frorna constant-tension"operation to a high-speed reeling-in operation,switch 16 is opene d to deenergize cal loadfrom the alternator -'ll4,"sothat its rotor 19 can be turned idly conjointly with rotor- 17 ofmachine 13. Switch 36 is then opened,'and switch 38 is closed to motor13 and switch 9 is opened'to remove'all electristator windings 7 topower supply 8 by closing switch; 9; second, conventionalpaying-outoperation,by:con-

connect leads 39 and together, so'thatYthe stator winding 7 of motor 5issubstitutedfor tht re'sistive load 18' onfthe windingslof rotor-17;Underthese' conditions no powefr is supplied to the winch motor 5.

"Closing of the switch 'l6 would tend to .turn rotor 17 in the clockwisedirection indicated by the arrow. Closingof reversing switch 37, ontheother hand, would tendto turn the rotor 17, in theoppositei orcounterclockwise directionl If switch isclosed at the same time,however, the squirrel-cage vrnotor-34 will actually effect rotation ofrotor l7;of electrical machine 13 in the clockwise direction.

[\lihile a squirrel-cage, induction motor isnot a synchrono us motor;it. is virtu'ally a; cbn'stant-speed motor in that itsspeed isreducedonlyslightlyatfull loadover its speed under no load-Consequently,the electrical fieldin the stator winding 15 of the, electrical machine1 I3 is rotating in aficounterclo ckwis'edirection at approximately thesam e.speed that the rotorwindings l7 3 are being rotated mechanicallyin the clockwise direc-' tion. Since both of these rotationsare theresultof C 'deanemann current'finput, currentwillbegener ated in thewindings-of the rotor 17 at a frequency equal to the algebraic sum oftherotating electrical field and the rotating rotor windingsforapproximately 120 cycles.By impressing'the 120-cycle alternating speedat which it would rotate if switch .38 were'open necessary for theinduction motor 34 and the electrical machine 13 to be matched so thatthe nominal speed of the induction motor is approximately equal to thes'tant-tension-type of operation to the high-speed reeling-in operationifthe switch 35 isclosed before the switch 16 is opened and the switch37 closed.

For constant linetension operation the rotor. 17 of the electricalmachine 13 would be rotating in the a clockwise direction the same as itwould be rotating whendriven by motor 34 during high-speed reeling-in.Consequently, there would be noappreciable. mechanical shock in changingfrom one type of operationto the other. Also, torqueis applied to thewinchmotor wind ing -7 in the reeling-indirection under constant-tensionoperation, so, if the line 2 were castoff, the motor 5 I a would begintopick up speed in thefreeling-in dired tion.. Substitution of powergenerated bythe: coils of rotor 17. for power" generatedbythe-statorcoils 20 of alternator l4would simply accelerate the winchmotor; 5 to the high-speed reeling-in conditionjmore rapidly,

because the motor would be operatingunder light load.

' With the mechanism illustrated in FIG.;1, therefore,

a choice of four 'typesof operation isavailable, namely,v

first, conventional reeling-in operation byz connecting nectingfstatorwindings 7 to power supply 8 byclosing switch 10; third,constant-tension operation by connectingstator windings 7 to thealternator 14 by closing a i I switch 9'; and, fourth, high-speedreelingin by c onf necting stator windings 7 to rotor windings 17byclosing switch 38 with switches 36, 9,, 9'. and l0 open when l V suchrotor is driven positively by thesquirrel-cage induction motor 34.

FIGS. 2 and 3 illustrate anadaptatio n of the same general type ofmechanism shown asbeing utilized on a mg 1 in towing barge brage 1" by aline 2'. Such line is wound on a drum 4' on the stern of the tug and hasa bridle connected to towing bitts 3' on, the barge. The

lected by clos'ingswitchfi orswitch 10 to connect the stator 7 of themotor to the supply line 8 for effecting rotation of the motor in thereeling-in direction or paying-out direction, respectively. When thedesired length of towing line has been established, the switch I 9*or 10is opened, and the switch 9' is closed to connect the stator coils 70fthe winch motor tothe output'lines f 21 connectedto the stator coils 20of thealternator 14. I

By driving the rotor 19 of thej'alternatorby the rotor 17 of thepolyphase'phase-wound induction motor 13, 5

Y substantially constant tension can be maintained in the currentgeneratedby the windings of rotor 17 ontothe stator windings 7 ofthemotor 5, such motor will rotate in the reeling-in direction atapproximately twice the towing line 2' despite uncoordinated pitchingand heaving of the tug andbarge resulting" from heavy weather. e I

In towingoperations, however,yitis also desirable to maintain the lengthof the towing line 2 substantially constant within reasonable limits,although it is' much I more important thatjthe tensionzfor'ces in theline'be maintained substantially constant rather'kthan ,the length of.the line beingkept constant; The present'in-f vention includesaprovision for maintainingthe length l of the tow line constant withinreasonable limits, as well rotor fieldexcitationcurrent sourceaspreventing substantial fluctuations in the towline tension. For thispurpose a scope' or line-length sensor 39 is connected to the winch drum4.

The, essentialcomponent of the scope. sensor 39 is a rheostat which isadjusted automatically. from a selected value in response to rotation ofthe winch drum 4'.The winch drum'arid rheostat are connected by suit:

able gearing, or other suitable mechanical connection, I

so that as the drum turns in thereeling-in direction the resistance willbe increased, whereas .when the line pays out the resistance will bedecreased. This resistance is connected byleads42 and43 in the circuitof the DC In addition, a manually adjustable rheostat 40 is connected byleads "41 and 42 in series with the scope sensor rheostat 39.

[when the desired length of towline 2' has been selected, the manuallyadjustable rheostat 40 is turned until the tension in towline 2" hasbeen established which will'maintain the desired lengthof towline undersmooth towing conditions for the particular barge, barge load and towingspeed;v If the weather or seas tend to separate the tug and the tow, thetowing line will lengthen. The scope sensor will beactuatedautomatically in response to paying-out rotation of the drum 4' todecrease the resistance of the rheostat 39, so that a larger excitationcurrent will flow to the rotor 19 of the alternator, causing aliighervoltage output from the stator winding 20, resulting in'thewinch motor 5developing a greater torque.

The greatertorque applied by the winch motor 5 to the'drum 4, will,ofcourse, increase the tension in.tow-' ing line 2' somewhat, tending toreel'the' line in. Such increase in line tension will, however, begradual and I progressive rather than abrupt. As the line is reeled in,the rheostat of the scope sensor will be adjusted auto- 1 matically toincrease the resistance of the 'rheostat'39 As shown in FIG. 2, thissystem is equipped with the high-speed reeling-in accessory shown inFIG. 1. As explained in describing the operation of the mechanism shownin that figure,"when the operation of the motor is converted from aconstant-tension operation to a high-speed reeling-in operation, switch16 is opened to deenergize motor 13 and switch 9' is opened. Opening ofsuch switch removes all electrical load from theal ternator 14 anditsrotor 19 can simply be turned idly conjointly with rotor 17-ofmachine 13. Consequently, any adjustments'of the scope sensor rheostat39 effected by rapid rotation of the. drum 4' has no effecton .thealternator 14 because ofthe open-circuit condition of its field winding20. t

The rapid retrieval of the lineaccomplishedby highspeed rotation of thewinch 4' can then be effected as described previously by openingswitches 36 and closing switches 37, and 38. Such operation will impress120 cycle alternating current generated by the windings of rotor 17 ontothe stator winding 7 of motors to effect its rotation at high speed.

While FIGS. ;1 and show representative circuit diagrams, therelationship of physical componentsofthe system is portrayed to betteradvantage in FIG. 3. The

ships power supply 8 can be connected to a main control panel 24containing suitable fuses. andnperhaps,

switches 9 and 10. The automatic control panel 25 may be connected tothe main control panel which, in turn,

is also connected to the winch motor 5 and the brake 6. To suchautomatic control panelis connected the alternator 14 by a circuit 21.The alternator drive control I 26 is connected to the motor 13.,and mayinclude the again to its initial value as the towing line is restored toits original length. I

Conversely, if the towing line should tend to slacken,

the winch drum 4' will rotate in the reeling-in direction which willturn the scope sensor rheostat 39 in the direction to increase theresistance in the rotor field excitation circuit. Such increase inresistance will decrease the excitation current, causing the outputvoltage from the stator windings 20 to be reduced. The resultantreduction in torque applied by the'winch drum motor 5 to the winch drumwill enable the towing line 2 to pay out until the scope sensor rheostatagain has been adjusted to its initial resistance value. The'more thetow ing line varies in length, of course, the greater will be theadjustmentof the scope sensor rheostat-39, and the alteration in torqueon the winding drum4'effected by the motor 5 will vary correspondingly.Consequently thegreater the change in length of the towing line which iseffected, the greater will be the alteration in tension of the towingline in a sense tending to restore the line to its original'lengthj Inaddition to adjusting the tension of towingline 2 automatically toinduce restoration of the initial towing 7 line length,.a visual oraudible alarmcan be providedto be actuated. by movement of the rheostat39mincrease or to decrease the resistance mor'ethan a predeterminedamount. The pilot is thus alerted to the pres- 'ence of alteredoperatingconditions so that he can sup.- plement the effect of the scope sensor39 my manuallyadjusting rheostat 40.

switches;16 and'37. The resistance grid bank l2"for the winch motor isconnected to. the automati'c control panel 25 and the calibratingresistance grid bank 18' for the alternator .drive motor, if it is ofthe phasewound inductance type, is connected to the alternator ing insteps the amount of the resistances 12' effec tively connected to thewindings of rotor 11 through a the bridging circuit 12'. The controlleralso has a hamdle 28 operable to controlclosing of switches 16 and- 9 insequence, or opening of switches 16, 9'; and 36 and closing of switches35, 38 and 37 in sequence.

In use, handle 27 can be swung in one direction to. close switch 9 forinitiating energization of the winch motor 5 with the mai rimumamount ofresistances 12 r in the circuit. Continuedmovement of such handle in thesame direction through successive steps will reduce 7 progressively theamount of resistance 12' effectively in the circuit of rotor 11 so astoincrease the speed or torque of thewinch motor. If the handle 27, ismoved in the opposite direction past its central position, it willeffect opening of switch 9 and closing of switch 10 to effect'reversalofthe. direction of rotation of motor 5. Continued movement offthe handle27 in such reverse direction will progressively decrease the amount ofresistance 12 effectively in the circuit of the motor rotor ll'so asto'increase thespeed or torque of the motor. After the handle 27 hasbeen restored to central off position, handle 28 canbe "moved into aposition I f to close switch 16 for the purpose of starting the drivemotor 13 for alternator 2 mm the motor is started, the handle can bemoved farther into'automatic position.'Handle 27 can .thenbe moved intothefirst position inwhich maximum-resistance 12' is included in thecircuit of rotor 11 of motor Next-the handle canbe moved stepi-by-stepinto, positions in which'the amount ofresistance 12' in the circuitofnwinch motor rotor 11 isreduced progressively-by effecting shifting ofthe bridging connections:125; n- 1 v t The effect of such manipulationof the controls on the operation of the winch4 under automaticVconditionis that when thehandle 27 is in the first'position the winch motor 5will drive the winch 4 to reel in line if the line pull is less than aselected value. As the line pull increases and the'rnechanical torque ofwinch 4 and winch motor 5 increases correspondingly, the speed .of themotor 5 and winch 4: decreases until they r t are stopped at theconstanttension linepull. If the line pull increases beyond that value,line will be unreeled from the winch drum, t 1 I When thecontroller-handle 27 is set in the second position, the same type ofoperation ensues, except that ,the critical valuejofline pullwill bealteredJIf the tension in line 2 should decrease below this value, themotor 5 will drive the winch 4 in a reeling-in direction until thatvalue of linetension is reached. If the line tension should increaseabove thatvalue, line will be paid out at a speed depending uponthc'tension of the line until such tension has been reduced again to thecritical value. If the controller is shifted to the third position,

the critical valuejof line tension will be still higher. If

i the controller handle27fis moved to the fourth position, the criticalvalue ofline tension again-will be in creased. In each case, the motorand winch; drum will be rotated to pay out or reel in'line as may benecessary to restore the selected critical value of line tension forwhich the controller is set;

, T10 as are the switches, 9,1 10, 1 6, 3 '5,,36,37,'38 and19".. No

complexrelay. or circuit-breakersystem is required, ale though relays toprovide for, remote control by the handles 27 and 28 are neededandnormal fuses or overload conditions occur which would alter the linepullf'lf the line pull drops below theselected value, thus reducing theload on the variable-frequency AC source;8', the

frequency will increase, thus automatically increasing the poweravailable to thewinch motorforexpediting winding-in rotation of thewinch 4 torestore the line I tension tothe' predetermined value.Thus,the previous condition of the line tension is restored without apple--ciable hunting or overtravel. a Power utilized is minimum becausedrivingmovementof equipment iseffected only'as and when-.necessary torestore the selected line tension. Despite the tendency of the automaticsystemto-maintairi its stability; the selectedlineftension can be variedeasily and instantaneously, or .the automatic mechanism can be,

rendered inoperative and the winch motor immediately placed under manualcontrol to effectvolunt ary-rota tion of the winch drum in eitherdirection, without reference to linepull, lclaim:

1. In line-tensioning mechanism including linewinding means connected toa line, an electric line-.

winding means motor continuously connected to supply continuousmechanicaltorqueto the line-winding meansfor winding in such linewhenever the mechanical torque on the line-winding means produced by theY line tension tends to drop below the mechanical torque produced on theline-winding means bythe' line- When the apparatus. is us'edfor towing,it will beconj venientto mount thecontroller for rheostat 40 on theremotely located controller standard as shown in FIG.

I '3. Such rheost atadjustment will then be readily availwinding meansmotor, an electric power source nor- I mally continuously connected tothe line-winding means motor to provide electric, current theretocontinuously for producing mechanical torque on the linewinding meanstending to reel in'line whether theline winding means motor is-stopped'or turning in a lineable to the pilot for changing" the output ofalternator F14 toenabIe the lengthof the towingline to be increased orto decrease the length of such line, depend-' ing upon whether thetowing line has shortened or lengthened excessively. I

Even when the motor and winch are stopped, power is. being consumed.Also, the higher the line pull and torque, the greater will be the loadon the variablefrequency AC source; 8 and, consequently,the lower willbe the frequency and voltage. Such reduction in frequency and voltagewill, of course, be the result of the reduction inspeed of the motor.l3in a motor- .alternator type of AC source. The power consumed I when thewinch motor and winch are not moving generates heat and, consequently,it may be desirable to provide suitable meansjfor cooling the motor andresistance grid banks 12" and 18 and, perhaps, the motor 13 andalternator 14. Such cooling mechanism'is represented by a fan 30 shownin FIG. 3 which would be energized whenever the switch'9 is closed.

The winch motor 5, alternator drive motor 13, alter- I nator 14 andmotor 34 are allof standard construction,

reeling-in direction or turning in the line-paying Out direction, andload-responsive means responsive to the electric current load on theelectric power sou'rceresulting from the mechanical torque produced bythe line-winding means motor on the line-winding means" and operable tovary an output characteristic of the electric power source automaticallyin response t vari-j ation in mechanical torque exerted by theline-winding means motor on the line-winding means resulting fromchanges in line' load and corresponding variation in electric currentload on the electricpower source, the improvement comprising theelectricpower source including a first alternatornormally connectedtosupply electric currentto the"line-winding means motor, an t t 1alternating current electrical machine having a wound v I rotor,operableselectively asa motor and as a second 1 alternator and mechanicallyconnected to drive said first alternator when operating asa motor, means(for electrically disconnecting said first alternator from theline-winding means motor and connecting the rotor winding of saidalternating current electrical machine to the line-winding means motorwhen said electrical machine is operating as a second alternator, anddriving means connected to said alternating currentelectri cal machinefor driving the rotor thereof mechanically "when said machineisoperating'as a second alternator.

#2.-In the line-tensioning mechanism defined in claim I l, the drivingmeans being continuously connected me- 11, the driving means including asquirrel-cage induction motor.

i 4. In] the line-tensioning mechanism defined inclaim 1, thealternating current electrical machine being a phase-wound inductionmachine including a stator winding and a rotor winding, one of saidwindings being connected to the line-winding means motor toserve as apower supply therefor, and an alternating current supply connected tothe other winding of the electrical machine.

5; In the line-tensioning mechanism defined in claim 4, the drivingmeans including a squirrel-cage induction motor electrically connectibleto the same alternating current supply that is connected to thealternating current electrical machine.

6. In the line-tensioning mechanism defined in claim l, and means forcontinuously mechanically connecting the rotor of the first alternatorand the rotor of the alternating current electrical machine.

$33 3? UNITED STATES PATENT OFFICE CERTIFICATE OF I CORRECTION .ffgg ngNo. 3- ,774 ,88 3 q 7 Dated November '27, 197.3

e It is certified that error appears in the abeveidentifi ed p ateritthat. said Lettez s Patent are hereby cotrected as shown below z elrCQIumn 3, -1 in'e' 10 cancel "mount" and insert l-amount-{g .line I 63,after "'in'terconnected" insert f-through swifc 'ch36*.:. Column1ine'38, cance1"'FIGS. .2 and 3 'illu st ret'e" aid-insert f;

,--;EIG. 2' illustrates". I 1 v I 5 Column 7, 1inef1'2,f,cance1 "'of"and, insert betweent he rotor lyi gn d q, $3 .9 l e 18th! g n 19m. 1

(SEAL) Attest;

EDWARDFMJLETCHERQT-Tmf 1 c.*mnsmtn ummy; Atdeeting Off'i'cer e I I VConmiesion'r of, -;P.a1;e1r115s, I

. mg UNITED STATES PATENT OFFICE 1 CERTIFICATE OF CORRECTION 1 am No.3,774,883 Dated November 27, 1973 lnventofls) Cyrus W. Ostrom Itiscertified that error appears in the above-identified patent end thatsaid Letters Patent are hereby corrected as shown below:

ifColumn 3 line 10 cancel "mount" and insert --amountline 1 63, after"'interconnected'f insert -through switch 36-: I

Column 6, line 38, cancel "FIGS. 2 and 3 illustrate" and insert -FIG. 2illustrates.

Column 7, line '12, cancel "of" and insert --botweerithe rotor field 19andn r v I H r r Signed and sealed this 18th day of June 19714..

(SEAL) Attest: r

EDWARD M.FLETcHER, JR.' Y c. MARSHALL 1mm Attesting Officer Commissionerof, Patents

1. In line-tensioning mechanism incluDing line-winding means connected to a line, an electric line-winding means motor continuously connected to supply continuous mechanical torque to the line-winding means for winding in such line whenever the mechanical torque on the line-winding means produced by the line tension tends to drop below the mechanical torque produced on the line-winding means by the line-winding means motor, an electric power source normally continuously connected to the line-winding means motor to provide electric current thereto continuously for producing mechanical torque on the line-winding means tending to reel in line whether the line-winding means motor is stopped or turning in a line-reeling-in direction or turning in the linepaying-out direction, and load-responsive means responsive to the electric current load on the electric power source resulting from the mechanical torque produced by the line-winding means motor on the line-winding means and operable to vary an output characteristic of the electric power source automatically in response to variation in mechanical torque exerted by the linewinding means motor on the line-winding means resulting from changes in line load and corresponding variation in electric current load on the electric power source, the improvement comprising the electric power source including a first alternator normally connected to supply electric current to the line-winding means motor, an alternating current electrical machine having a wound rotor, operable selectively as a motor and as a second alternator and mechanically connected to drive said first alternator when operating as a motor, means for electrically disconnecting said first alternator from the line-winding means motor and connecting the rotor winding of said alternating current electrical machine to the line-winding means motor when said electrical machine is operating as a second alternator, and driving means connected to said alternating current electrical machine for driving the rotor thereof mechanically when said machine is operating as a second alternator.
 2. In the line-tensioning mechanism defined in claim 1, the driving means being continuously connected mechanically to the alternating current electrical machine for driving of the driving means by the alternating current electrical machine when the alternating current electrical machine is operating as a motor.
 3. In the line-tensioning mechanism defined in claim 1, the driving means including a squirrel-cage induction motor.
 4. In the line-tensioning mechanism defined in claim 1, the alternating current electrical machine being a phase-wound induction machine including a stator winding and a rotor winding, one of said windings being connected to the line-winding means motor to serve as a power supply therefor, and an alternating current supply connected to the other winding of the electrical machine.
 5. In the line-tensioning mechanism defined in claim 4, the driving means including a squirrel-cage induction motor electrically connectible to the same alternating current supply that is connected to the alternating current electrical machine.
 6. In the line-tensioning mechanism defined in claim 1, and means for continuously mechanically connecting the rotor of the first alternator and the rotor of the alternating current electrical machine. 